Surface-mounted electronic components such as connectors having leads extending from main insulating bodies for direct connection by reflow soldering to the conductive layers or paths on a printed circuit board, are well known.
As shown in FIG. 7, a known surface-mounted connector 50 comprises a main body 51 and a series of lead portions 52 which extend away from a rear side of the main body 51 and have remote ends adapted for surface-mount connection with respective conductive layers 54 of a printed circuit board 53.
In recent years, the inexorable trend to miniaturization with increasing complexity leads to an increasing requirement for ever higher densities of packing electronic parts on printed circuit boards with significantly reduced pitches of leads 52 and conductive layers 54.
However, as the pitch of the conductive layers 54 is reduced, any variation in the pitch leads 52, for example, deformation by bending inadvertently, or imprecise installation of the connectors on the printed circuit board 53 provides a significantly increased risk of the leads 52 contacting adjacent layers 54. This imposes a practical limit on the closeness of the pitch, making it difficult to install electronic parts at high densities.
Furthermore, there is an increasing tendency for the printed circuit boards 53 to be thinner, also increasing risk of deformation by warping with a consequential increase in variation of the pitches of the leads and in the risk of the leads 52 unintentionally contacting an adjacent conductive layer 54.
Additionally, if board warping occurs, there is an increased risk of poor contact pressure between the ends of the leads 52 and the conductive layers 54, during the surface mounting.
Surface-mount connection is conventionally performed by installing connector 50 on the printed circuit board 53 with respective leads contacting reflow solder pads overlayed on the conductive layers 54 and heating the assembly in a furnace or oven thereby melting the solder layers so that the respective leads located thereon are connected to the conductive layers by the molten solder.
In the event of board deformation, such as warping, when the connector is located on the printed circuit board for soldering, some of the leads 52 may become separated from the conductive layer 54, (float on top of the layer), with the result that, even if the reflow solder layer on the conductive layers of the board is melted, the molten solder may not contact such leads 52 with consequential faulty connection. Furthermore, since the circuit board itself is also subject to the heat from the furnace or oven, the possibility of heat deformation of the circuit board increases still further increasing the risk of poor connection.